Speed ratio shift method

Abstract

The present invention essentially concerns a method for a motor vehicle speed ratio shift. Said method uses a power transmission device ( 1.1 ) comprising a traction chain consisting of a heat engine ( 2 ), a clutch ( 3 ), an electrical machine ( 4 ), a gearbox ( 5 ), and wheels ( 6 ). The invention is characterized in that, upon shifting, the heat engine ( 2 ) is started before, during or after the torque (CMEL) observable on the shaft ( 11 ) of the electrical machine ( 4 ) is canceled, by means of a starter system ( 7 ) mechanically independent of the electrical machine ( 4 ).

1. Method of shifting gear ratios of a vehicle utilizing a power transmission device having a heat engine and an electrical machine, this electrical machine being connected firstly to the heat engine through a clutch and secondly to a shaft of wheels through a gearbox, said method comprising, in order to start the heat engine when both an order to start the heat engine and an order to perform a gear shift have been issued and the heat engine is off at a time the order to perform a gear shift is issued:
 (i) starting the heat engine using a starting system connected to the heat engine and mechanically independent of the electrical machine, while the vehicle is being powered by the electrical machine alone, 
 (ii) performing the gear shift, 
 wherein the performance of the gear shift comprises:
 canceling a detectable torque on the shaft of the electrical machine, 
 making the rotation speed of the electrical machine converge toward a target speed before the new gear ratio is engaged, and 
 engaging a new gear ratio, and 
 
 (iii) coupling the heat engine and the electrical machine via the clutch after performing the gear shift, 
 wherein, when the order to start the engine is prior to the order to shift gear ratios, and a time period between the prior order to start the heat engine and the subsequent order to shift gear ratios is less than a threshold time period (TS) corresponding to a time needed for the heat engine to start and to couple with the electrical machine, the method comprises:
 authorizing the heat engine to start, but 
 delaying the coupling between the shaft of this heat engine and the shaft of the electrical machine as long as the new gear ratio has not been engaged, 
 
 so that the starting system dissociates the starting of the heat engine from the gear shifting of the vehicle. 
 
     
     
       2. Method according to  claim 1 , wherein the coupling of the heat engine and the electrical machine via the clutch comprises:
 maintaining the clutch, which was disengaged up to a time of engaging a new gear ratio, disengaged while the new gear ratio engages, and 
 engaging the clutch after the engagement of the new gear ratio. 
 
     
     
       3. Method according to  claim 2 , wherein:
 the shaft of the heat engine is coupled with the shaft of the electrical machine while torque is reactivated. 
 
     
     
       4. Method according to  claim 2 , comprising:
 making each of the heat engine and the electrical machine converge toward an optimal setpoint torque in terms of the heat engine fuel consumption, after coupling the shaft of the heat engine with the shaft of the electrical machine. 
 
     
     
       5. Method according to  claim 1 , wherein:
 the threshold time period (TS) is approximately 350 ms. 
 
     
     
       6. Method according to  claim 1 , comprising:
 once the heat engine has started, allowing the heat engine to run through some initial compression strokes in order to be autonomous, and then cutting off the starting system. 
 
     
     
       7. Method according to  claim 1 , wherein:
 the heat engine is started before the detectable torque on the shaft of the electrical machine is canceled. 
 
     
     
       8. Motor vehicle configured to perform the method according to  claim 1 . 
     
     
       9. Method according to  claim 1 , wherein:
 the heat engine is started while the detectable torque on the shaft of the electrical machine is being canceled. 
 
     
     
       10. Method according to  claim 1 , wherein:
 the heat engine is started after the detectable torque on the shaft of the electrical machine has been canceled.